TWM508122U - Photodiode structure - Google Patents

Abstract

A photodiode structure includes a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer. The second semiconductor layer is disposed on the first semiconductor layer. The second semiconductor layer has a side surface. The side surface has an upper portion, a lower portion, and a central portion connected to the upper portion and the lower portion. The central portion substantially forms a plane. The third semiconductor layer is disposed on the second semiconductor layer. An extending plane extended from the central portion divides the third semiconductor layer into a first body and a first protrusion. The first protrusion extends from the extending plane toward a direction opposite the first body.

Description

Light diode structure

This creation is about a light diode structure.

Photodiode is a photodetector that converts light into a current or voltage signal depending on the mode of use. A common traditional solar cell generates electricity through a large area of photodiode. The photodiode is substantially similar to a conventional semiconductor diode, except that the photodiode can be exposed directly to the source or through a small transparent window or optical fiber package to allow light to reach the light sensitive area of the device to detect the optical signal. Many of the PIN structures used to design photodiodes (ie, stack structures of n-type semiconductor layers, intrinsic semiconductor layers, and p-type semiconductor layers), rather than the general PN junction, increase the response speed of the device to the signal. Light diodes are often designed to operate in a reverse biased state.

When the photodiode is in operation, if a photon with sufficient energy hits the photodiode, it will excite an electron, which will generate free electrons (and a positively charged hole). Such a mechanism is also referred to as an internal photoelectric effect. If the absorption of photons occurs in the depletion layer of the PIN structure, the internal electric field in the region will eliminate the barrier between them, so that the hole can move toward the anode and the electrons move toward the cathode, so Photocurrent is generated. Since the actual measured photocurrent is the sum of the leakage current (the current generated when the photodiode is in operation and not illuminated) and the illumination generated current, the leakage current must be minimized to improve the device's light. Sensitivity.

The present invention provides a photodiode structure for reducing leakage current generated during operation of the photodiode structure.

According to an embodiment of the present invention, a photodiode structure includes a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer. The second semiconductor layer is disposed on the first semiconductor layer, wherein the second semiconductor layer has a sidewall having an upper portion, a lower portion, and a central portion connecting the upper portion and the lower portion, and the sidewall portion of the central portion substantially forms a plane. The third semiconductor layer is disposed on the second semiconductor layer, wherein the extending plane of the central portion extending upwardly divides the third semiconductor layer into the first body and the first protrusion, and the first protrusion extends from the extending plane to the first body The outer side extends.

In one or more embodiments of the present invention, the first semiconductor layer is an n-type semiconductor layer.

In one or more embodiments of the present invention, the second semiconductor layer is an intrinsic semiconductor layer.

In one or more embodiments of the present invention, the third semiconductor layer is a p-type semiconductor layer.

In one or more embodiments of the present invention, the thickness of the first semiconductor layer is about 200 to 500 angstroms (Å).

In one or more embodiments of the present invention, the thickness of the second semiconductor layer is about 10,000 to 15,000 angstroms (Å).

In one or more embodiments of the present invention, the third semiconductor layer has a thickness of about 200 to 800 angstroms (Å).

In one or more embodiments of the present invention, the first body has a first top surface, and the first protrusion has a second top surface, the first top surface being adjacent to the second top surface.

In one or more embodiments of the present invention, the second top surface extends from the plane of extension to an outer side relative to the first top surface by about 100 to 500 angstroms (Å).

In one or more embodiments of the present invention, the distance the first protrusion extends from the plane of extension to the outside of the first body increases substantially as its height increases.

In one or more embodiments of the present invention, the extending plane extending upward from the central portion divides the second semiconductor layer into a second body and a second protrusion, and the second protrusion extends from the extending plane to the second body. The outer side extends, and the first protrusion connects the second protrusion along the extending plane.

In one or more embodiments of the present invention, the distance from the extending plane to the outside of the second body extends from the extending plane to the distance from the extending plane to the outside of the first body. small.

In one or more embodiments of the present invention, the distance that the second protrusion extends from the plane of extension to the outside of the second body increases substantially as its height increases.

The above embodiment of the present invention forms a photodiode by causing the first protrusion to protrude slightly from the first body and form a bird's beak structure. In a reactive ion etching process of bulk structure, the first protrusions will block plasma ions that may directly impinge on the sidewalls of the photodiode structure. Therefore, the sidewall structure of the photodiode structure will not be destroyed, thereby greatly reducing the leakage current generated by the photodiode structure during operation.

100‧‧‧Light diode structure

120‧‧‧First semiconductor layer

130‧‧‧Second semiconductor layer

131‧‧‧ upper

132‧‧‧Central Department

133‧‧‧ lower

134‧‧‧Second ontology

135‧‧‧Second protrusion

140‧‧‧ third semiconductor layer

141‧‧‧ first ontology

143‧‧‧First top surface

144‧‧‧First protrusion

145‧‧‧second top surface

190‧‧‧Extension plane

200‧‧‧Substrate

210‧‧‧ top surface

300, 400‧‧‧ curve

FIG. 1 is a cross-sectional view showing the structure of an optical diode according to an embodiment of the present invention.

FIG. 2 is a diagram showing a leakage current intensity-time diagram of the photodiode structure and the conventional photodiode structure according to an embodiment of the present invention.

FIG. 3 illustrates the leakage current intensity of the photodiode structure and the conventional photodiode structure according to different embodiments of the present invention.

In the following, a plurality of embodiments of the present invention will be disclosed in the drawings. For the sake of clarity, a number of practical details will be described in the following description. However, it should be understood that these practical details are not applied to limit the creation. That is to say, in the implementation part of this creation, these practical details are not necessary. In addition, some of the conventional structures and elements are shown in the drawings in a simplified schematic manner in order to simplify the drawings.

FIG. 1 is a cross-sectional view showing a photodiode structure 100 in accordance with an embodiment of the present invention. Different implementations of this creation provide a Light diode structure 100. The photodiode structure 100 is mainly used for (medical) X-ray digital flat panel sensors. Specifically, the photodiode structure 100 is used to fabricate a pixel unit of an X-ray digital flat panel sensor.

As shown in FIG. 1 , the photodiode structure 100 is disposed on the substrate 200 . The photodiode structure 100 includes a first semiconductor layer 120, a second semiconductor layer 130, and a third semiconductor layer 140. The second semiconductor layer 130 is disposed on the first semiconductor layer 120, wherein the second semiconductor layer 130 has a sidewall having an upper portion 131, a lower portion 133, and a central portion 132 connecting the upper portion 131 and the lower portion 133. The sidewall portion of the central portion 132 is substantially A plane is formed which is substantially perpendicular to the top surface 210 (or horizontal plane) of the substrate 200. The third semiconductor layer 140 is disposed on the second semiconductor layer 130, wherein the extending plane 190 extending upwardly from the central portion 132 divides the third semiconductor layer 140 into the first body 141 and the first protruding portion 144, and the first protruding portion 144 The extension plane 190 extends toward the outside of the first body 141.

Specifically, the first semiconductor layer 120 is an n-type semiconductor layer, the second semiconductor layer 130 is an Intrinsic semiconductor layer, and the third semiconductor layer 140 is a p-type semiconductor layer. Thus, the first semiconductor layer 120, the second semiconductor layer 130, and the third semiconductor layer 140 form a PIN structure.

In the formation of the photodiode structure 100, a reactive ion etching process is generally used. However, in this process, plasma ions may impinge on the sidewalls of the photodiode structure 100 (eg, upper portion 131, lower portion 133). And the central portion 132) destroys the sidewall structure of the photodiode structure 100, thereby causing the photodiode structure 100 to be produced during operation A large leakage current is generated.

Specifically, in the reactive ion etching process, a negative bias is first generated under the substrate 200, so that the plasma ions vertically move from the top to the bottom due to the attraction of the negative bias, and impinge on the photodiode structure 100. The film layer is to be etched and an omnidirectional etching effect is produced. After the plasma ions strike the layer to be etched, the plasma ions contact and chemically react with the layer to be etched, thereby producing an isotropic etching effect.

However, the foregoing is only a description of the ideal situation. In some cases, the plasma ions may directly impinge on the sidewalls of the etched film layer in the photodiode structure 100, thereby destroying the sidewall structure of the photodiode structure 100.

To this end, the third semiconductor layer 140 has a first body 141 and a first protrusion 144 , and the first protrusion 144 extends from the extension plane 190 toward the outside of the first body 141 . Because the first protrusion 144 is slightly protruded from the first body 141 and forms a Beak Type structure, the first protrusion 144 can block the direct impact on the sidewall of the photodiode structure 100. Plasma ion. Therefore, the sidewall structure of the photodiode structure 100 will not be destroyed, thereby greatly reducing the leakage current generated by the photodiode structure 100 during operation.

Specifically, the material of the first semiconductor layer 120, the second semiconductor layer 130, and the third semiconductor layer 140 may be tantalum or niobium. It should be understood that the materials of the first semiconductor layer 120, the second semiconductor layer 130, and the third semiconductor layer 140 are merely exemplified, and are not intended to limit the present invention. The first semiconductor layer 120 and the second semiconductor layer 130 may be elastically selected according to actual needs. The material of the third semiconductor layer 140.

The first semiconductor layer 120 may have a thickness of about 200 to 500 angstroms (Å). It should be understood that the thickness of the first semiconductor layer 120 is merely exemplified, and is not intended to limit the present invention. Those skilled in the art of the present invention can flexibly select the first semiconductor layer 120 according to actual needs. The thickness.

The second semiconductor layer 130 may have a thickness of about 10,000 to 15,000 Å. It should be understood that the thickness of the second semiconductor layer 130 is only exemplified, and is not intended to limit the present invention. Those skilled in the art can flexibly select the second semiconductor layer 130 according to actual needs. The thickness.

The third semiconductor layer 140 may have a thickness of about 200 to 800 Å or 200 to 400 Å. It should be understood that the thickness of the third semiconductor layer 140 is only exemplified, and is not intended to limit the present invention. Those skilled in the art can flexibly select the third semiconductor layer 140 according to actual needs. The thickness.

Specifically, the first body 141 has a first top surface 143, and the first protrusion 144 has a second top surface 145 that is adjacent to the second top surface 145. Furthermore, the first top surface 143 and the second top surface 145 may together form a plane.

As shown in FIG. 1 , the second top surface 145 extends from the plane of extension 190 to an outer side relative to the first top surface 143 by about 100 to 500 angstroms (Å). Alternatively, the second top surface 145 extends from the extension plane 190 to an outer side relative to the first top surface 143 by about 200 to 400 angstroms (Å). Or, the second top surface 145 extends from the extension plane 190 to an outer side relative to the first top surface 143 by about 200 to 300 angstroms (Å).

Specifically, the distance that the first protrusion 144 extends from the extension plane 190 toward the outside of the first body 141 substantially increases as its height increases.

In addition, the extension plane 190 also divides the second semiconductor layer 130 into a second body 134 and a second protrusion 135. The second protrusion 135 extends from the extension plane 190 toward the outside of the second body 134, and the first protrusion The second protrusion 135 is connected along the extension plane 190.

Specifically, the distance from the extension plane 190 to the outer side of the second body 134 from the extension plane 190 is smaller than the distance that the first protrusion 144 extends from the extension plane 190 toward the outside of the first body 141. The distance that the second protrusion 135 extends from the extension plane 190 to the outside of the second body 134 substantially increases as its height increases.

In summary, the first protrusion 144 and the second protrusion 135 together form a protrusion shaped like a triangular cylinder.

Both the photodiode structure 100 and the conventional photodiode structure are formed using a reactive ion etching process, however, the first protrusion 144 and the second protrusion 135 of the photodiode structure 100 must be formed under specific parameters. Specifically, the reactive ion etching process should have a pressure of 70 to 120 millitorr (Millitorr), a radio frequency output (RF-Output) of 1200 to 1400 watts (Watt), and sulfur hexafluoride (SF ₆ ). The gas inflow rate should be 200 to 460 sccm (Standard Cubic Centimeter per Minute), and the inflow rate of hydrogen chloride (HCl) gas should be 350 to 780 sccm.

It should be noted here that the first protrusion 144 and the second protrusion 135 of the photodiode structure 100 are formed in a reactive ion etching process, and may hinder the light diode structure 100 directly after formation. Plasma ion of the sidewall.

In addition, the reactive ion etching process may be used again in the subsequent related process of the photodiode structure 100, and at this time, the first protrusion 144 and the second protrusion 135 will again function to block the direct impact of the photodiode structure. The function of the plasma ion of the 100 side wall.

The foregoing description of the structure of the photodiode structure 100 is not only applicable to one side of the photodiode structure 100, and the other side of the photodiode structure 100 may have the same structure as described in the foregoing structure.

FIG. 2 is a diagram showing a leakage current intensity-time diagram of the photodiode structure 100 and the conventional photodiode structure according to an embodiment of the present invention. As shown in FIG. 2, the curve 300 represents the relationship between the leakage current intensity and the time of the photodiode structure 100 of the present invention in the operating state, and the curve 400 represents the leakage current intensity and time of the conventional photodiode structure in the operating state. relationship. From Fig. 2, we can find that after the state of the photodiode structure 100 and the conventional photodiode structure is stabilized (i.e., the time is longer than 100 seconds), the leakage current intensity of the photodiode structure 100 is about 30 fA/pixel, while the conventional The leakage current intensity of the light diode structure is about 60fA/pixel. Thus, the leakage current intensity of the photodiode structure 100 is reduced by about 50% compared to the leakage current intensity of the conventional photodiode structure.

Figure 3 illustrates a photodiode according to various embodiments of the present creation The leakage current intensity of the bulk structure 100 and the conventional photodiode structure, wherein the sampling panel number 1 to the sampling panel number 6 are conventional photodiode structures, and the sampling panel number 7 to the sampling panel number 10 are light dipoles of different embodiments. Structure 100. As shown in FIG. 3, after the state of the photodiode structure 100 and the conventional photodiode structure is stabilized, the leakage current intensity of the conventional photodiode structure is almost greater than 60 fA/pixel, and the photodiodes of different embodiments are different. The leakage current intensity of the bulk structure 100 is about 30 fA/pixel. From this point of view, it is indeed possible to stably and effectively reduce the leakage current intensity by providing the bird's beak structure to the photodiode structure 100.

In the above embodiment, the first protrusion 144 is slightly protruded from the first body 141 and forms a bird's beak structure. Therefore, in the reactive ion etching process for forming the photodiode structure 100, the first protrusion is formed. 144 will be able to block plasma ions that may strike directly into the sidewalls of photodiode structure 100. Therefore, the sidewall structure of the photodiode structure 100 will not be destroyed, thereby greatly reducing the leakage current generated by the photodiode structure 100 during operation.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any person skilled in the art can make various changes and refinements without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

100‧‧‧Light diode structure

120‧‧‧First semiconductor layer

130‧‧‧Second semiconductor layer

131‧‧‧ upper

132‧‧‧Central Department

133‧‧‧ lower

134‧‧‧Second ontology

135‧‧‧Second protrusion

140‧‧‧ third semiconductor layer

141‧‧‧ first ontology

143‧‧‧First top surface

144‧‧‧First protrusion

145‧‧‧second top surface

190‧‧‧Extension plane

200‧‧‧Substrate

210‧‧‧ top surface

Claims (13)

An optical diode structure comprising: a first semiconductor layer; a second semiconductor layer disposed on the first semiconductor layer, wherein the second semiconductor layer has a sidewall having an upper portion, a lower portion, and a connection a central portion of the upper portion and the lower portion, a sidewall of the central portion substantially forming a plane; and a third semiconductor layer disposed on the second semiconductor layer, wherein the central portion extends upwardly and one of the extending planes The third semiconductor layer is divided into a first body and a first protrusion, and the first protrusion extends from the extending plane to the outside of the first body. The photodiode structure of claim 1, wherein the first semiconductor layer is an n-type semiconductor layer. The photodiode structure of claim 1, wherein the second semiconductor layer is an intrinsic semiconductor layer. The photodiode structure of claim 1, wherein the third semiconductor layer is a p-type semiconductor layer. The photodiode structure of claim 1, wherein the first semiconductor layer has a thickness of about 200 to 500 angstroms (Å). The photodiode structure of claim 1, wherein the second semiconductor layer has a thickness of about 10,000 to 15,000 Å. The photodiode structure of claim 1, wherein the third semiconductor layer has a thickness of about 200 to 800 Å. The photodiode structure of claim 1, wherein the first body has a first top surface, and the first protrusion has a second top surface, the first top surface being adjacent to the second top surface. The photodiode structure of claim 8, wherein the second top surface extends from the plane of extension to an outer side relative to the first top surface by about 100 to 500 angstroms (Å). The photodiode structure of claim 1, wherein the distance from the extending plane to the outer side of the first body is substantially increased as the height thereof increases. The light diode structure of claim 1, wherein the extending plane extending upwardly of the central portion divides the second semiconductor layer into a second body and a second protrusion, and the second protrusion extends from the second protrusion The plane extends toward an outer side of the second body, and the first protrusion connects the second protrusion along the extending plane. The photodiode structure of claim 11, wherein a distance from the extending plane to the outer side of the second body is greater than the first protruding portion from the extending plane to the first The outer side of a body extends a small distance. The photodiode structure of claim 11, wherein the distance from the extending plane to the outer side of the second body increases substantially as its height increases.